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authorLuke Nelson <lukenels@cs.washington.edu>2020-04-30 19:02:09 -0700
committerDaniel Borkmann <daniel@iogearbox.net>2020-05-04 17:04:42 +0200
commitcf48db69bdfad2930b95fd51d64444e5a7b469ae (patch)
tree5949744e14c415cf767d9009771de173ecb8d544 /arch/arm/net
parent60bcbc41ffb35572288681f41d1d8ab8bdb98841 (diff)
bpf, arm: Optimize ALU64 ARSH X using orrpl conditional instruction
This patch optimizes the code generated by emit_a32_arsh_r64, which handles the BPF_ALU64 BPF_ARSH BPF_X instruction. The original code uses a conditional B followed by an unconditional ORR. The optimization saves one instruction by removing the B instruction and using a conditional ORR (with an inverted condition). Example of the code generated for BPF_ALU64_REG(BPF_ARSH, BPF_REG_0, BPF_REG_1), before optimization: 34: rsb ip, r2, #32 38: subs r9, r2, #32 3c: lsr lr, r0, r2 40: orr lr, lr, r1, lsl ip 44: bmi 0x4c 48: orr lr, lr, r1, asr r9 4c: asr ip, r1, r2 50: mov r0, lr 54: mov r1, ip and after optimization: 34: rsb ip, r2, #32 38: subs r9, r2, #32 3c: lsr lr, r0, r2 40: orr lr, lr, r1, lsl ip 44: orrpl lr, lr, r1, asr r9 48: asr ip, r1, r2 4c: mov r0, lr 50: mov r1, ip Tested on QEMU using lib/test_bpf and test_verifier. Co-developed-by: Xi Wang <xi.wang@gmail.com> Signed-off-by: Xi Wang <xi.wang@gmail.com> Signed-off-by: Luke Nelson <luke.r.nels@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20200501020210.32294-2-luke.r.nels@gmail.com
Diffstat (limited to 'arch/arm/net')
-rw-r--r--arch/arm/net/bpf_jit_32.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index bf85d6db4931..48b89211ee5c 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -860,8 +860,8 @@ static inline void emit_a32_arsh_r64(const s8 dst[], const s8 src[],
emit(ARM_SUBS_I(tmp2[0], rt, 32), ctx);
emit(ARM_MOV_SR(ARM_LR, rd[1], SRTYPE_LSR, rt), ctx);
emit(ARM_ORR_SR(ARM_LR, ARM_LR, rd[0], SRTYPE_ASL, ARM_IP), ctx);
- _emit(ARM_COND_MI, ARM_B(0), ctx);
- emit(ARM_ORR_SR(ARM_LR, ARM_LR, rd[0], SRTYPE_ASR, tmp2[0]), ctx);
+ _emit(ARM_COND_PL,
+ ARM_ORR_SR(ARM_LR, ARM_LR, rd[0], SRTYPE_ASR, tmp2[0]), ctx);
emit(ARM_MOV_SR(ARM_IP, rd[0], SRTYPE_ASR, rt), ctx);
arm_bpf_put_reg32(dst_lo, ARM_LR, ctx);